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B. D. WILLIS.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED FEB.28.I916.

1 ,3 1 4,778 Patented Sept. 2, 1919.

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AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED ran. 2a. 1916.

l ,3 1 4,778 Patented Sept. 2, 1919.

4 SHEETS-SHEET 2.

EH51" nag B. D. WILLIS.

AUTOMATIC TELEPHONE SYSTEM.

APPLICAIION FILED rmza. 1916.

1,314,778. Patented Sept. 2, 1919.

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KWWW @(MQW HUM" may [rzuenfur B. D. WILLIS.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED FEB. 28, I916.

1 ,3 1 4,778. Putentvd Sept. 2, 1919.

4 SHEETS-SHEET 4.

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ianmmrm n. winms, or CHICAGO, rumors, assieivoa T0 AUTOMATIC ELECTRIC comrnrw, or cnrcaeo 'innmois, A conrom'rron or nmnvoxs.

AUTOMATIC TELEPHONE SYSTEM.

To all whom it may concern:

Be it known that I, BERNARD D. Wnius,

a citizen of the United States of America, and a resident of Chicago, county of Cook,

'andState of Illinois, have invented certain be established by operators, such as rivate branch exchange operators; or whic comprise, in part at least, measured service lines provided with meters.

In systems of the above general character, it has been found desirable, in inter-ex- 'change connections, to operate the automatic switches in the distant exchange over so-called simplex circuits superimposed upon the connecting trunk lines. It is desirable also, or even necessary, to rovide means as sociated with the inter-exc ange trunk lines, whereby supervisory signals may be operated to notify operators of the response of called subscribers. Furthermore, where "measured service is given, means must be provided for actuating the meters associated with calling lines at the proper time.

his the principal object of my invention to provide a trunk circuit having a superim- P l I poses; and having, in addition, facilltles for posed simplex circuit for operati controlling supervision at an operators p0 s1t1on,'or for controlling subscribers meters or slmllar devices.

A further object of my invention is the provision of a trunk circuit of the above description adapted for two way service.

-Further objects of my invention relate.

to circuit improvements of various kinds whereby the above features are incorporated intowell known types of apparatus to form a complete and eflicient system.

To accomplish the foregoing and other useful ends my invention comprises means which will be hereinafter fully explained,

reference being had to the accompanying drawings, in which Figure "1 shows a diagrammatic layout of the telephone system chosen to illustrate my invention, while Figs.

Specification of Letters Patent.

Application filed February 28,1918. Serial No. 80,619.

Patented Sept. 2, 1919.

2, 3, 4, and 5, taken in order with the lines at the ends thereof in alinement, represent a complete circuit connection between two subv switches E. The selectors E, associated with both manual and automatic lines, have access to repeaters F which are arranged to transmit impulses over simplex circuits superimposed upon the trunk lines T to control automatic selectors E and connectors H in the exchange Y.

The automatic telephones A, through the medium of their individual line switches C, and the manual telephones A, through the medium of theprivate branch exchange I switchboard M, have access to selectors E at exchange Y, whereby connections may be extended to repeaters F to control automatic selectors E and connectors H over the same trunk lines T.

Referring to Fig. 2, there is shown at A a subscribers substation which may be of any suitable type and as herein represented comprises a receiver 2, transmitter3, switch book 6 and ringer 4. The line conductors 10 and 11 terminate in a private branch exchange switchboard where they are provided with line and cut-oifrelays 8 and 9, answering jack J, and one or more multiple jacks J The private branch exchange switchboard may be provided with a plurality of cord circuits such as theone indicated by reference character 0. Cord circuit 0 comprises essentially the answering and calling plugs P and P, the supervisory lamps 19 and 21, controlled, respectively, by relays 15 and 18, listening key K, ringing key K and calling device key K. Relay 18 1s a polarized relay the o eration of whosearmature depends upon t e direction of current flow in the relay windings.

Reference character 20 indicates a calling device which is preferably common to a plurality of cord circuits and adapted to be 20 adapted to be 30' ing,

40 change bridged across any one of them through the medium of the associated key K. The calling device maybe of any suitable type, such, for

- example, as the one shown in Britlsh patent to S. G. S. Dicker, No. 29654 of 1910.

An outgoing trunk line extends. from the jack J at the private'branch exchange to the main exchange X,-where it terminates in the selector switch E which, as repre- 9 sented herein, is of the same general type of selector switch as is disclosed in U. S. Letters Patent No. 815,321, granted March 13, 1906, to Keith, Erickson and Erickson; be-

ing, however, of the particular type disclosed in British patent to the Automatic Telephone Manufacturing Company, No.

2543 of 1914. Among other details the selector E comprises a bank of contacts arranged in horizontal rows or levels and engaged by a set of wipers 31, 32, and 33, carried upon a shaft (not shown) which has a vertical movement controlled by the vertical magnet 23 and a rotary move? ment controlled by the rotary magnet 24.

25 The operation of the various parts of the are slow to release their armatures after their energizing circuits are broken. f The selector E has access, through certaln of its bank levels, to groups of trunk lines extendin to the different line groups in exand, in addition, through a separate bank level, to a group of trunk-lines extending to exchange Y. One trunk line in this latter group is shown extending from the bank contacts 31 and 33 in Fig. 2, by

way of conductors 46 and 47, repeater F (Fig. 3), repeating coil I, jack J conductors 87 and 88, jack J (Fig. 4), repeating coil Z, )and repeater F to connector H (Fi 0 Tie repeater .F comprises a plurahtyof relays whose functions can best be described in connection with the detailed explanation. It may be mentioned at this time, however, that relay is an electropolarized relay, it

55 being provided with a polarizing winding'of high resistance and few turns. Current flowing in the polarizing winding is not of itself .sufficient to operate the armature but is able to prevent .such operation by the other winding unless the current therein flows in the proper direction.

It will be seen that the trunk conductors 8788 are looped through springs of jacks J 2 and J 3 before connecting with the repeating coils associated with repeaters]? and F.

Means for restoring the.

The oif normal contacts 34 and,

This is not, of course, necessary in carrying usual drops 57 and 90, and, in addition, with visual busy signals 59 and 89, and sleeve relays 58 and 91.

Repeater F, located in the exchange Y, is in all respects similar to repeater F. Conductors 77 and 79 are shown as extendingto the connector H, which is of the general type of connector switch disclosed in U. S. Letters Patent No. 815,176, granted March 13, 1906, to Keith, Erickson and Erickson; being, however, of the particular type disclosed in British patent to the Automatic Telephone Manufacturing Company, No. 2270 of 1914. The connector H com prises among other details a bank of contacts arranged in horizontal rows or levels and adapted to be engaged by a set of wipers 60, 61, and 62 carried upon a shaft (n'ot shown) having a vertical movement controlled by the vertical magnet 64 and rotary movement controlled by the rotary magnet 65. The usual side switch comprising the wipers 110, 111,112, and 113 is controlled by the private magnet in the well known manner. The operation of the various parts of the switch is controlled by the double wound line relay 63. There is rovided also a release magnet 68, a back bridge relay 66, a busy test relay 72, and a ringing relay 69, whose functions are well known. Contacts 114 and 115 are, closed only when the switch shaft has been raised one or more steps from its normal position. Relays 67 and 71 are slow acting,

i. 6., they are slow to release their armatures after their respective energizing circuits are broken.

While I have shown, for the sake of simplicity, the conductors 77 and 79 as extending directly to the connector H, it will be understood that selector switches such as the selector E (Fig. 2) may be interposed between the repeater F' and the connector H in order to increase the capacity of the system.

The connector switch H has access to a group of lines among which is the line extending to substation A The automatic substatlon A may be of any suitable type, it being only required that the controlling impulses be sent by interrupting the line circuit rather than by 'groundin conductors. Such a substation is lllustrated in British patent specification No. 2543 of The individual line switch C, whose func- "70 and Y exchanges and are provided withthethe line tion is to extend the line of substation A when calling to an idle selector switch, is of the general type of line switch disclosed in British patent to'R. W. J ame's, No. 26301 of 1906; being, however, of the particular type disclosed in U. S, Letters Patent to F. New,- forth, J r., No. 13,901, reissued April 13,1915. The line switch '0 will have access to selector switches E as is shown diagrammatically in Fig. 1 through the medium of which connections may be extended to other lines in the exchange Y or to lines in exchange X, as previously mentioned.

Before proceeding farther it will be advisable toreturn to the trunk circuit and explain certain details which it was not convenient to mention before. In Fig. 2 there is shown a'set of multiple bank contacts dc:

noted by reference characters 35, 36, and 37 These contacts may be located in the bank of a selector switch E which is accessible to line switches C in exchange X (Fig. 1). In Fig. 3 there are shown two conductors, 77' and 7 9, extending upward from the repeater F. These conductors are similar to conductors 77 and 7 9 (Fig. 4) and extend either to a-'selcctor switch or' a connector switch dependingon the capacity of exchange X. In Fig. 1, trunk lines such as the one represented in Fig. 3 by conductors 77 and 7 9 may be seen extendin downward from repeaters F to selectors The repeater F (Fig. 4) 's accessible to two groups of selector switc es as shown clearly in diagrammatic drawing Fig. 1. This fact is indicated in Fig.- 4 by the showing of two sets of multiple contacts numbered, respectively, 848586 and 81-82-83. These two sets of ontacts correspond to the two j sets shown at the right of Fig. 2.

For supplying current for operatin 'and talking purposes I have shown a plura ty of batteries, indicated by reference characters B, B and B", each having its positive pole grounded. There are also shown two, other batteries, B and B each having its negative pole grounded and whose functions will be fully described hereafter. The reference character Q indicates a busy signaling machine, whose function is well known.

Having given a general description of the apparatus, I will now describe the operations performed in the process of establishing a connection from the manual substa tion A (Fig. 2) to the automatic substation A (Fig. 5'). Since the automatic selectors, connectors, and other apparatus, herein represented, are in general well known in the art, and are fully described in the publications' hereinbefore referred to, their operation will be described in a more or less general manner.

Upon the removal of the receiver at the calling telephone A the circuit of the line relay 8 is closed over a path which extends from ground G through the back contact of armature 14, line conductor 10, receiver 2, transmitter 3, spring 7 on hook 6, line conductor '11, armature 13 and its back contact,

.and the relay.8 to the battery B The relay 8, upon energizing, closes the circuit to lamp 12 to indicate to the operator that a the jack J, whereby the connection is completed between the line and the cord 0. By the engagement of the third conductor of the plug P with the sleeve of jack J, the circuit of the cutoff relay 9 is closed in series with relay 16 of the cord; .The relay 9, upon energizing, disconnects the line relay 8 from the line and connects the armatures 13 and 14 with their front contacts. The subscriber is now provided with talking current from the battery B. through the two relays 15 and 17 The relay 15, upon energizing,

opens the circuit of supervisory lamp 19 which was closed at another point when relay 16 energized. The operator then connects her talking set across the cord through the medium of the key K, and upon learning from the calling subscriber that a subscriber at the distant automatic exchange Y -a circuit is closed for-line relay 22 of the selector E in series with the polarized relay 18 of the cord circuit 0. This circuit extends from ground through the lower winding of linerelay 22,-through normally closed contacts of relay 26, ring of jack J and plug P, springs 41 and 42', relay 18, Zsjprings 42 and 41, tip of plug P and jack through another pair of normally closed contacts of relay 26, and thence through the upper winding of line relay 22 to the battery B. The polarizedrelay 18 is energized and attracts its armature in the direction to close its contact, which lights the supervisory signal 21 over a circuit that is obvious. The line relay 22, upon energizing, closes the circuit of the slow acting relay 27. The relay 27, upon energizing, pens the circuit of the release magnet 25, and prepares a circuit for the vertical mag net 23 and the rotary magnet 24 inthe well known manner.

and substitutes for the former springs 43 and 43' which lead to the'calling device 20. The relay 18 will now be in an open circuit and upon denergizing will open the circuit of lamp 21. The relays of the selector are unaffected by the operatio of The operator now. throws the key K, which separates springs 42 and '42 from springs 41 and 41', respectively,

60 -aifiThis circuit extends from ground the key K, owing to the make bef ore break contacts of said key. The operator now operates her calling device in accordance with the number of the desired station, which will be assumedto be220. Upon the operation of the calling device for the first digit 2, the impulse springs of the calling device are separated twice momentarily, each time breaking the circuit of the selector line relay 22. Since the relay 27 is slow acting it docsnot deenergize during the momentary interruptions of its circuitby the deenerglzations of the line relay 22. Therefore each time that the line relay deenergizes an impulse of current istransmitted through the vertical magnet 23- and slow relay 29. The vertical magnet thus receives two impulses and operates 'to raise the shaft wipers 31, 32,

' and 33 two steps to a position opposite the second level of. bank contacts. The. slow relay 29 is operated by these'impulses to close the circuit to the test relay 28 which, upon energizing, locks up to ground G: and further prepares a circuit for the rotary magnet 24. -When the slow relay 29 deeners gizes, after the first group of impulses have been completed, it closes a circuit to the rotary magnet 24 through interrupter springs relay 26 which, upon energizing, removes tends from ground upon the test contact to,

the relay 22 from the circuit and connects the line circuit with the wipers 31 and 33. If this trunk line is busy, however, the pri- .vate wiper 32 finds the test contact with which it engages provided with a guarding ground potential and another circuit is closed to maintain relay28 energized before its circuit is broken by the energization of the rotary magnet. This last circuit exthe private wiper 32 through themiddle and front springs of relay 28 thence through said relay 28 to the battery B. The relay 28 is thus held energized and prevents the switching relay 26 from energizing. From the foregoing it will be clear that when the .wipers 31, 32, 33 arrive at idle trunk'contacts the controlling relay 28 is deenergized and closes acircuit to switching relay through springs 30, sprin s 24", ofl normal contact 40, springs 39 an .said relay 26 to battery "B. As before stated the switching relay 26, upon energizing, disconnects the relay 22 and switches the line circuit to the wipers 3'1 and 33 whlch extends the connection to the line relay 44 of the repeater F,

line relay 44 of the repeater F extends from ground G through the lower winding of said relay 44,.conta'ct springs 116 and 117, conductor 47 w1per 33, contact springs 171 of relay 26, ring of jack J and plug P,

springs 42 and 43, calling device 20, --springs 43 and 41, tig of plugP and jack J, contact springs 1 0 of relay 26, wiper 31, conductor 46, springs '1-18 and 119 of relay 49, and the upper winding of line relay 44 to battery B. The line relay 44, upon energizing, prepares a circuit for slow relay 49 at springs 120 and closes a circuit for release relay 45, as before mentioned, extending from ground G through springs 121 and said relay 49 to the battery. Relay 45 at its springs 122 provides the before mentioned holding ground to the selector switching relay 26 over a' path extending from ground G through contact springs 122, release trunk conductor 48, wiper 32, springs 39 of relay 28, thence through relay 26 to the battery B.

The relay 56 energizes at this time over a circuit extending from ground G through springs 122, along conductor 127, springs 128 and the said relay 56 to the battery B. The relay 56, upon energizing, removes the drop relay 57 from the trunk line by opening contacts 129 and 130 and lights the busy lamp 59 over. a circuit. which extends from ground G" through springs 131 and the" lamp 579 to the battery B. A further result of the energization of relay 45 is the shifting of spring 123 out of contact with spring 124 and intoengagement-with spring 125 thereby completing a circuit for slow acting relay 49 which extends from the nongrounded pole of thebattery B through said relay 49, springs of relay 44, springs and 123, along conductor 126 to the junction of repeating coil windings I and I thence over-both windings I and If in multiple, springs of jackJt, line conductors 87 and 88 in multiple, springs of jack J 8 (Fig. 4), windings Z and Z of repeating coil Z in multiple to their. junction, thence.

along conductor 102, springs 103 and 104 of relay 101 of repeater F, conductor 106, relay circuit'as traced includes relay 49 of repeater F (Fig. 3) and relay 96 of repeater F (Fig. 4). The relay 49 is. so constructed and adjusted that it will not operatively energize at this time and it requires current of 96, springs 108 and 109 to ground G". This reater strength than that furnished by the attery B to enable it to pull up its armature. The relay 96 energizes and upon doing soseparat'es springs 129 and 130 and forces spring 129 mto contact with spring 131. A circuit is then closed which includes slow relays 97 and '99. This circuit extends from ground G through springs 129. and 131 and relays 97 and 99 in multiple to the battery B A further result of the energization of relay 96 is the closure of springs 132 thereby bridging the impedance 93 in series with the upper winding of electropolarized relay 94, across the conductors 77 and 79 leading to the connector (Fig. 5). The relays 97 and 99 both energize over the circuit as above traced. Relay 99, upon energizing, forces springs 133 mto contact,

thereby preparing a circuit for slow relay 95. A further result of the ene rg1zat1 on of relay 99 is the closure of a c1rc u1t extending from ground G through spr1ngs'134, 135, and 136 and the lower winding of the electropolarized relay 94 to the battery B.

Both windings of the said relay 94 now carry current which flows in opposite directions and they partially' neutralize each other, there is therefore no resultant attraction ofthe armature. A still further result of the energization of relay 99 is tlreprovision of ground upon the private bank conremoves, by the opening of contacts 140 an 141, the drop 90 from, across the trunk 11 ne conductors 87 and 88. By the closure of its springs 142 the circuit to the busy lamp 89 iscompleted. This circuit extends from ground G through springs 142 and said lamp 89 to battery B 'The slow relay 97, upon energizing, forces the springs 143 and 144 out of contact with springs 1.45 and 146 and into contact with springs 147 and 148,

respectively. The result secured. thereby is that the repeating coil windings Z and Z are disconnected from the selectorbank contacts 81 and 86 and their multiples and are connected instead to the line conductors 77 l and 79 leading to the connector H.. By this arrangement it is seen that repeating coil Z condenser C and repeating coil Z are now in multiple with impedance 93 and upper f winding of relay 94 across the trunk conductors 77 and 79.

As hereinbefore stated, when relay 96 energized a bridge comprising the impedance 1 93 and upper winding of relay 94 was comthose versed in the art that I may have the the cut-off relay 92 to battery B The relay 92, upon energ zingi minimum while the impulses are being pleted across the trunk to the connector line rela 63, whose complete circuit now exten s from ound through the lower windm of said me relay 63, contacts of springs 14 and 148, line conductor'79, springs 132 of relay 96, upper winding of relay 94, impedance coil 93, return line conductor 77, springs 149 and 150 and the upper winding of the line relay 63 to the battery B. The line relay 63 is energized over this circuit and operates to close a circuit to the release relay 67 which extends from ground G through spring 151 and its front contact, and relay 67 to the battery B Relay 67, upon energizing, opens the. circuit of the release magnet 68 at springs 152 and 153 and forces s ring 153 into contact with spring 154 there y preparing a circuit for the vertical magnet 64. .A further result of the energization of rela 67, is the closure of springs 155 there v supplying ground Gr along conductor 78 WlllCh is without function in the layout herein illustrated. It is, however, well understood by trunk line conductors terminate in a selector switch such as the switch E instead of leading direct to the connector as herein shown. In that event the ground Gr over release conductor 78- would maintain the selector in its operated position after the connector has been selected. In this connection it is well tonote again that I may. provide a plurality of selectors between the repeater v and connector H, thus increasing the capacity of the system without deviating from the principles of my invention. The switching operations up to this point were responsive to the first digit called by the operator at the cord circuit 0.

The operator now operates the calling device for the second digit 2, thereby causing the line relay 44, of repeater F, to'deenergize twice; momentarily. The relay 45 being slow acting, remains in its energized position during the momentary interruptions of its circuit, so that each time the line relay 44 deenergizes and separates the springs 120 the circuit including relay 49 of repeater F and relay 96 ofrepeater -F is momentarily broken. Relay 49 as before stated does not operatively energize and is provided with a copper slug for the a purpose of reducing its impedance to a transmitted therethrough over the simplex circuit to the distant repeater F. Relay 96 of repeater F, responds to the momentary interruptions of its circuit and is momentarily de'e'nergized a number of times to repeat impulses to the connector H. The relay 96, at each deenergization, opens the circuit of relays 97 and 99 and closes the circuit of relay 95. Relays 97 and 99 being slow acting maintain their armatures in an 1 energized position while their circuit is momentarily 'openeds- When the first impulse -is transmitted and .the relay 96 deenergizes to. repeat said impulse a circuit is closed which extends from ground G", through springs 129 and 130, sprlngs 133 and the relay 95 to'the battery B The relay 95 being slow acting maintains its armature in an energized position during thesucceeding interruptions "corresponding to the impulses of the group and in its energized position short circults, at sprlngs 15-6, the impedance 93 and upper winding of relay 94. A short time after the group of impulses have been transmitted the re-. lay '95. again deenergizes and separates spring-S156. During the t1me that relay 95 is energized, impulses aretransmitted by the relay 96 to the connector lmefrelay 63 over a circuit which extends from ground through the lower winding of line relay. 63 through springs 147 and 148, km condu'ctor 79, springs 132-of relay-96, springs 156 "of relay 95, return line conductor 7 springs 149 and 150 and the upper winding of the line relay 63 to the battery'B I11 response to interruptions of the above circuit, line relay 93" is-momentarily denergized a number of times; release relay 67,

however, being slow acting, maintains its armature in the attracted position during two impulses over this circuit and operates to raise the shaft wipers 60, 61;, and 62 two momentarily deenergizations of relay 63.

Each time the line 63 deenergizes', an im-- pulse of current is transmitted to the vertical magnet'64' over a circuit which extends "from ground G through spring 151 and its back contact-,- springs 15-3 and 154, private control relay 71, vertical magnet-64, side switch wiper 113 (in 'first position) to the battery B. The vertical magnet recelves steps to a position opposite the second level. of contacts. The relay .71 is energized by these impulses and operates to close a circuit extending from ground G",

, through springs 157 and the private mag- 3 net 70 tolthebattery B The relay 71, being slow acting does not allow its armature to fall backunti l after the last impulse et,

has been delivered to the verticallma when it breaksfthe circuit to the private magnet 70 which. in turn" denergizes' and permits the side switch to pass to the second position. The side switch wiper in passing from first to second poslt on transfers the battery connection from the vertical magnet 64 to the rotary magnet 65.

. Theoperator, at the cord circuit 0, now

o erates the calling device 20 for the last digit 0, whereby the energizing circuit of the connector line relay 63 .is broken ten times in the same manner as previously described. Each time the relay 63- denergizes an' impulse of current is transmitted through spring 151 and its back contact, springs 153 and 154, relay 71, springs 158 over a circuit extending from ground G of relay 72, rotary magnet 65, side switch wiper 113, (in second position) to the battery B The rotary magnet operates in response to these. impulses to step the wipers 60, 61, and 62 ten steps onto the contacts of the desired line, while the relay 71 operates in the same manner as for the previous digit to advance the'side switch another step, i. e fromsecond to third position, after the last impulse of the series is delivered. The movement of the side switch wipers 110 and 111 to third position completes the line connection with the called telephone. The wiper '112, upon reaching third position, establishes a guarding groundpotential at the connector-private bank contacts of the called line and also provides an ener 'zing circuit for the cut-off windlng 75 o the 'subscribers individual switch 0'. This circuit extends from ground Gr through the sideswitch wiper 112, private wiper 61 and cut-olfwinding 75 to the'battery B The cut-01f winding, upon energizing, removes the'line relay 7 6 from the called subscribers line. The side switch. wiper 113 on passing to third position completes the circuit of the ringing relay 69 which extends from ground Gr through interrupter 74, ringing relay 69, springs 158 of rela 73, side switchwiper 113 (in third position) to the battery B. The .relay 69, .upon energizing, operates to disconnect the calling line from the called line, and to. bridge the ringing current generator R across the called line to signal the called subscriber. Since the cirestablished. The' relay 18 again energizes ,to close the circuit of supervisory signal 21 as hereinbefore stated, When the subscriber at the-called telephone A removes his receiver, or as soon thereafter "as the ringing relay 69 deenergizes, ifiit happens to be energized at the time, said telephone .is provided with talking current; over a circuit extending from groundthrough the left handwinding of the back bridge relay 66, springs 160 ofprivate magnet 70, thence over heavy conductors to back contacts of ringing relay 69, linewiper 62 toand through the substation A, back over-the osition, whereby the calling de-- other side of the line to wiper60, another set of back contacts of. ringing. relay 69, over heavy conductor to springs. 161 of private magnet .70 and through the right tween the windmgs'of the line relay 63 and the trunk conductors 77 and 79 whereby the direction of current flowing in the up-' per winding of relay 94 is reversed. This reversal of current in the upper winding of relay 94, causes said relay to attract its armature to shift spring 108 out of contact with spring-109 and into contact with spring 107, whereby the battery B 1s inserted in series with the battery B (Fig. 2). .These batteries have their opposite poles grounded and will produce an increased flow of current which is sufiicient to operatively' energize the marginal relay 49 of repeater F. Relay 49, upon energlzmg, transposes the connections between the windings of line relay 44 and the trunk line conductors 46' and 47, whereby the direction of current flowing in the trunk line is reversed. Polarized relay 18, being in-.

cluded in this circuit operates to open the circuit of the supervisory signal 21 and the lamp is extinguished. In this manner the operator is notified that the called man has answered.

A further result of the energization of relay 66 upon the response of the called subscriber is-the closing of a circuit to cut-oil relay 73, which c'ircuit extends from ground G through side switch wiper 112, springs 1'62 and the said relay 73 to the battery B The relay .73, upon energizing, breaks the circuit of the ringing relay at springs 158 and closes a locking circuit for itselfthrough its springs. 159 independent of the springs 162 of relay 66, so that the ringing relay cannot be again energized unt1l the connector restores and makes another call. The subscriber at the manual substation A may now converse with the subscriber at the automatic substation A. The voice currents will travel over the heavy conductors and throu h repeating coils I and Z herein shown. fter the conversation is completed the operator is given a disconnect signal when the calling subscriberhangs up his receiver and another signal when the .called subscriber hangs up. When the calling subscriber hangs up, his line circuit is broken at spring 7, thereby open ng the circuit of relay 15 and'coil 17 Relay 15, upon deenergizing, closes the circuit of S'IJPGT'. I visory lamp 19.

J and J.

contact with spring 107 and intocontact with spring 109. The booster battery B is thereupon removed from the circuit of re-.

lays 96 of repeater F and marginal relay 49 of re eater F. Relay 49, owing to its margina adjustment, deenergizes and re-' verses the direction of current flow. to the polarized relay 18, which operates to move 1ts armature in 't e direction to close the clrcult of supervisory signal 21. The operator, percelving the disconnect signals, removes the plugs P and P. from the jacks By the removal of the lug P from ack J, the circuit of the cut-o5 relay 9 1s broken. Relay 9.;upon de'einergizi'ng, restpres the central 0 e uipment of, the calllng subscribers line to 1ts normal condltion. By the removal of the lug P from the jack J the circuit of the line relay 44 of repeater F is broken, which relay, upon deenergizlng, opens the circuit of relay 45 and also opens the circuit of relays 49 and 96 of repeaters F and F, respectively. Relay 45, upon deenergizing, removes theholdcausing the spring 108 to be shifted out of mg ground G, from the release conductor line and at springs 131 opens the circuit of busy signal lamp 59. Upon the removal of ground from the release conductor 48 the switching relay 26 of selector E de'elnergizes and closes the release magnet circuit which extends from ground G through the contact of springs 172, springs 38-, springs 173, off-normal springs 34 and the release magnet 25 to the battery B. .The release magnet 25, upon energizing, restores the switch to its normal condition and its own circuit is opened at springs 34 when the shaft reaches its lowest position. The relay96, upon deenergizing, opens the bridge across the trunk conductors 77 and 79 by separating springs 132. A further result of the deenergization of relay 96 is the separation of springs 129 and 131 and closure of springs 129 and 130, whereby relays 97 and 99 are de'nergized. Relay, 97, upon deenergizing, removes the repeating coil from across the trunk conductors 77 and 79 and connects said coil with the contacts of selector banks, which conditions normally ex ist. Relay 99, upon denergizing, opens the circuit of relay 95 which was closed when relay 96 de-' energized and also by the separation of springs 134,135, and 136 removes the guarding ground from the private contacts of the selector banks and opens the circuit of lower winding of relay 94. -A further result of the deenergization of relay 99 is the opening of the circuit of relay 92 which, upon deenergizing, again bridged the drop relay and condenserC across the trunk line and, at springs 142, opens the circuit of the V busy signallamp'89L, When the relay 96. de-' energizes and removes the'bridge across the,

trunk line 77 and 79 by separating springs 132,-the circuit offthe line relay 63 of connector H is broken. The relay 63, upon deenergizing,-fopens the circuit of, relay 67, which" upon 'deenergizing, closes the circuit of the release magnet '68 which was closed at another point by relay 63. The energizing .circuit of release magnet 68 extends from ground G through spring 151 and its back contact, springs 153 an 152, ofnormal contact 114 and the release magnet 68 to the battery 13*. The release magnet, upon energizing, restoresthe switch to its normal condition and its own circuit is opened at springs 114 whenthe switch'shaft reaches its lowest position. The releasing of the connector opens the circuit of 'cut-ofl winding 75 of the called subscribers m-. dividual switch 0' which, upon deenergizing, again places the line relay 76 under control of the substation A".

In the above description it'was assumedthat'the called line was idle and that connector H completed connection therewith. It will now'be explained how connection is prevented from being completed with a busy line and how theoperator is given a busy signal. Whenever a line is busy, either on account of having made a call or on account of having been called, its connector private banklcontac'ts are provided with a guarding ground potential. Therefore, when the private wiper 61 is rotated onto the contact of'the busy line and as soon thereafteras the slow relay 71 deenergizes, a connection 1s completed from ground upon said contact.

through the wiper 61, side-switch wiper 112 (in second position) springs 163 and 164, busy test relay 72, normally closed sprmgs of relay 71, and the private magnet 7 O to the battery B The private magnet 70 remains energized over this circuit and. maintains the side switch wipers in second position, thereby preventing 'the connection to the busy called line. The busy relay 72, upon energizing, opens the circuit of the rotary mag-- net at springs 158, disconnects ltself from the private wiper 61 and upon the engagement of its springs 165 and 164 completes a lock- I ing circuit for itself which extends from ground G through off-normal contact 115, springs 165 and 164, relay 72, no'rmally' closed's rings of relay 71 and the private magnet 0 to the battery B Upon the closure of springs 166, by-the energization of relay 2, a circuit is completed including the busy signaling machine Q which may be traced over the following path Ungrounded' pole of battery B secondary winding 167 of the induction coil, springs 166, 'side switch wiper 111 (in second position), line conductor 79, springs 148 and 144 of relay 97, winding Z of repeating .coil Z, condenser C,

' to the operator. I

When the called man answers, battery will windin Zof said repeating coi1,s rings I43 and '14 returnllne'conductor 7 springs 149 and 150, upper winding of the line relay 63 to the ungrounded 'ole of battery B, the startin point. The usy tonein passing throug the repeatlng coil windings induces a tone in windings Z and Z which flows over a circuit that extends from 'Windin Z, concontacts of jack J thence through windings I and I of repeating coil I, contacts ofjack J (along return toll line conductor 88, contacts of jack J and through winding Z "to winding Z. ,A' busy tone-is thus induced in windings I and I of repeating coil I which 'flows from windmg I through springs 168 of relay 51, trunk ,tacts of jack J over toll line con uctor 87,

conductor 46, l1newiper-31, springs 170 ofrelay 26, tip of jack J and tip of plug P,

springs 41 and 42 of key K, through contacts ofkey K to and through the operators set, back over contacts 42' and 41', ring of plug P and ring of jack J, springs 171 of relay 26, wiper 133, return trunk conductor 47, springs 169 of relay 51, winding I and condenser C to windlng I. The operator receives an audible buzz in her receiver over the above circuit and informs the calling subscriber that the called line is busy. The operator withdraws the plugs P and'P' from the jacks J and J which causes'the release of the apparatus in a similar manner to that hereinbefore described.

' It will be understood that I may provide telephone equipment arranged for measured service such as the automatictelephone equipment shown in British patent to Dicker, No. 1298 of 1910, or I may provide coin controlled telephone equipment such .as the type shown in United States Letters Patent to 'B. D.' Willis, No. 1,130,784, granted March 9, 1915. Either type of telephone shown in the aforesaid mentioned patents may bearranged in connection with a subscribers individual switch (such as the switch C" herein shown and referred to as similar to that 4 shownin United States Letters Patent to F. Newforth, Jr., No. 13,901, reissued April 13, 1915), toconnect .witha selector switch be reversed to the calling substation-if a measured service systeinto register the meter-ebut 'if a coin controlledsyst'em-to render his telephone inoperative fortalkhave been deposited.

apparatus is controlled by the calling auing purposes until the re uired coin or coins he release of the whereby an operator at one end of the line may manually signal an operator at the other end. By inserting a plug into the jack J 2 the spring contacts 174 and 175 are i opened, whereby the repeater is removed from the line and is prevented from being seized because of a guardingground potential being supplied from ground at G along release conductor 48 to the private bank contacts of the. selectors adapted to make connection therewith. When .a plu similar to the plu P of cord circu1t whose sleeve "conductor is connected to ground, is inserted into the jack J 2 a circuit 1s closed which extends from ground upon the sleeve of the plug through sleeve of jack J 2 and the relay 58 to the battery. Relay 58, upon energizing, closes the before mentioned circuit from ground G by way of contact -17 6, armature 128, conductor 127, and release conductor 48 to the selector private bank contacts. Having inserted a plug in jack J, the operator may project ringing current in the well known manner out over the trunk line to actuate the drop 90 at the distant exchange, thereby signaling an operator there stationed. By plugging into the jack J the called operator may converse with the calling operator and at the same time disconnect the automatic apparatus as described in the case of jack J After having finished with the connection the operator withdraws the plugs and the circuit conditions are again restored so that connection may be made in either direction manually, automatically or semiautomatically.

From the foregoing it is evident that have devised a very eflicient telephone system in which automatic connections are set up and controlled ove'r simplex circuits superimposed upon two way trunk lines.

Furthermore, it is obvious that I provide improved means responsive to the answering of the called subscriber for performing several functions, one of which is the controlling over a simplex circuit, of a supervisory signal at an operators board when the connection is established by the operator through the medium of her calling device and the automatic switches, Another function is the controlling, over a simplex circuit, of measured service devices or coin collectlng apparatus at a calling automatic "substation, when thesubscriber himself operates and controls the automatic switches.

While I have illustrated and described one particular embodiment of m invention, it is to be understood that I 0 not wish to be limited to the exact construction and arrangement of apparatus and circuits shown and described, but that various modifica-- tions can be made without departing from the spirit and scope'of my invention. What I claim as my invention is: 1. In a telephone system,means for connecting calling and called lines including a trunk line and an automatic switch, an

operating circuit for said switch including,

circuits each having two branches, a two conductor trunk line inductively connected at each end to one of said circuits connecting said exchanges, one of said branches of each circuit terminating in an automatic switch and the other terminating in a set of fixed terminals, an operating circuit for said switches including the two conductors of said trunk line in parallel, a relay associated with eachset of fixed terminals for controlling said operating circuit, a group of selector switches at each exchange adapted for seizing the set of fixed terminals thereat, means at each exchange for controlling a selector switch in the group there located to seize the associated set of fixed terminals and for operating the relay associated therewith, whereby said automatic switch at the other exchange may be operated through the medium of said operating circuit.

3. In a telephone system, two exchanges, circuits each having two branches, a two conductor trunk line inductively connected at each end to one of said circuits connecting said exchanges, one of said branches of each circuit terminating in an automatic switch and the otherterminating in a set of fixed terminals, an operating circuit for said switches including the two conductors of said trunk line in parallel, a relay associated with each set of fixed terminals for controlling said operating circuit, a group of selector switches at each exchange adapted,

automatic switch and for making the other' ductor trunk line inductively connected at each end to one of said circuits connecting said exchanges, one of; said branches of each circuit terminating an automatic switch and the other terminating in aset offixed terminals, anoperating circuit for said switches including the two conductors of said trunk line in parallel, a relay for controlling said operating circuit associated with each set of fixed terminals, a group of selector switches at each exchange, a manual switchboard associated with each exchange, and operator controlled means 'at each switchboard for operating a selector switch in the associated exchange to seize the set of fixed terminals there located and for operating the relay associated therewith, whereby said automatic switch at the other exchange maybe operated by way of sa1d operating circuit.

5. In a telephone system, two exchanges, a pair of circuits each having two branches, a two conductor trunk line inductively connected at each end to one of said circuits connecting 'said' exchanges, one of said branches of each circuit terminating in an automatic switch and the other terminating in a set of fixed terminals, an operating circuit for said switches mcluding the two conductors of said trunk line in parallel, a relay for controlling said 0 erating c rcuit associated with each set of xed terminals, a group change, with each exchange, each switchboard, operator controlled means at each switchboard for operating a selector switch in the associated exchange to seize the set of fixed terminals there located and for operatin the relay associated therewith, whereby said exchange may be operated by way of said operating circuit, and means controlled over said operating circuit from either exchange for operatin the signal at the switchboard associated with the other exchange.

6. In a telephone system, automatic switches, two exchanges, a trunk line' terminatin at each end in one of said automatic switc es connecting said exchanges, a controlling circuit superimposed on said trunk line and having at each end a normally connected branch containing a relay for controlling the automatic switch at that end, a source of current for said controlling cir; cuit, circuits at each exchange adapted for connection to said trunk line, supervisory signals associated with said circuits, a normally disconnected branch at each end of said of selector switches at each ex-" a manual switchboard associated.

a supervisory signal at calle I 'with said circuit and; controlled by the, "called line thereovcr for operating said relay automatic switch at the other-1 warm .co'ntrollin circuit containinga supervisory control re ay, means for connecting one of. said circu ts at either exchange" wlthjsaid trunk lme,.automatic means'jfor then substituting the normally disco" f1 branch at that exchange for the nornia y connected branch,,means associated withthe connected circuit at the one exchange for operating" the controlling, relay at the'other exchange by way of said controlling circuit, a second source of current, and" cans at the said other exchange for intro ucing said 'second ate the supervisory control relay the said first exchange.

7; Ina telephone system, a and 9.

called line, means for connecting said lines source in the said controlling circuit-tooperan operating circuit for said switch 4 by the called line thereoverfor operating said relay. v

8. In a telephone system, two exchanges each comprlsmg a plurality of lines, a two way trunk line between-exchanges, said trunk line provided with anautomaticswitch at each end, a circuitincluding two conductors of .said trunl; line in parallel for controlling said switches, a source of current for said circuit, means controlled ,by a calllng line in oneexchange for operatfmg the automatic switch in the other exchan e over said circuitfto connectwitha km, a relay, and me'ans'associated to reverse the direction" of current in the calling line. I

9. In a. telephone system, a calling and a called line, means forconn'ecting said lines including a 'trunk line 'and. an automatic switch, an operating circuit for said. switch superimposed upon talking" conductors, of'

said trunk line, a source of current for said circuit, means controlledrb y. the ,"calling line for operating said switchover said circuit to connect with the called "line, a relay for reversing the direction of current flow "over the calling line, means associated with s'aid circuit for operating said relay, said relay irresponsive to normal current in said circuit, said means for increasing the flow of current in said circuit to operate said'relay. 10. In a telephone system, two exchanges 7 each comprising a plurality of lines, a two way trunk line between exchanges, said trunk line, provided with an automatic switch at each'end, a circuit including two conductors of said trunk line in parallel for controlling said switches, a source of current for said clrcuit, means controlled by a calling line in one exchange for operating the automatic switch in the other exchange over said circuit to connect with a called line, a

- of current for said circuit, means controlled by'the calling line for operating said switch over said circuit to connect with thecalled line, a relay for'reversing the directlon of current flow in the calling line, means associated with said circuit for operatin said relay, said relay irresponsive to norma current in said circuit, a second source of current, said means'controlled by the called l ne for including said second source in sa1d circuit to operate said relay.

' 12. In a telephone system two exchanges each comprising a plurality of lines, a two way trunk line 'between exchanges, -sa1 d trunk line provided with 'an automatlc switch at each end, a CiI'Cllltdl'lCllldlIlg two conductors of Said trunk, line in parallel for controlling said switches, a source of current for said circuit, means controlled by a calling line in one exchange for operating the automatic switch inthe other exchange over. said circuit to connect with a called line, a relay for reversing the direction of current flow over the calling line, means associated with said circuit for operating said relay, said relay irresponsive to normal current in said circuit, a second source of current, said means controlled by thecalled line for including said second source in sald circuit to operate-Said relay. I

13. In a telephone system, an operators position and a trunk line accessible therefrom, an automatic switch, a seoondirunk line terminating in said automatic swltch, a third trunk inductively connecting the two, a circuit including two conductors of said third trunk line in parallel, a source of current for said circuit, means at the operators position forcontrolling said circuit by way of said first trunk line, means in sald circuit for controlling said switch by way of said second trunk line, a signal at said operators position, and a relay in said circuit for controlling said signal.

14. In a telephone system, a calling line, an operators position and a trunk line accessible therefrom, means at the operators position for connecting said Calling line and trunk line, a called line, an automatic switch, v

a second trunk line terminating in said automatic switch having access to. said called line,. a third trunk line inductivelyconnecting said first and second trunk lines, a circuit including two'conductors of said th1rd trunk line in parallel, a source of current for said circuit, means. in said circuit for controlling said switch by way of said second trunk line, means 'including said first trunk line for controlling said circuit from the operators position, whereby said switch may be operated to connect with the called 4 line, a signal at the operators position, and

a relay in said circult for controlling said signal.

15. position and a trunk line accessible thererom,

line terminatin in said automatic switch, a thirdtrunk in uctively connecting the two, a circuit including two conductors of said third trunk line in parallel, a source of current for said circuit, means at the operators position for controlling said circuit by way of said first trunk line, means in said circuit for controlling said switch by way of said second trunk line, a signal at said operators position, a relay in said circuit irresponsive to normal current therein for controlling said signal, and means for increasing the current flow in said circuit to operate said relay.

16. In a telephone system, a calling line, an operators position and a trunkline accessible therefrom, means at the operators position for connecting said calling lineand trunk line, a'called line, an automatic switch, a second trunk line terminating in said automatic switch having access to said called line, a third trunk line inductively connecting said first and second trunk lines, a circuit including two conductors of said third trunk line in parallel, a source of-current for said, circuit, means in said circuit for controlling said switch by way of said second .trunk'line, means including said first trunk line for controlling said circuit from the operators position, whereby said switch may be operated to connect .with the called line, a signal at the operators position, a relay in said circuit irresponsive to normal current therein for controlling said signal, and means for increasing the current flow in said circuit to operate said relay.

, 17. In a telephone system, an. operators position and a trunk line accessible therefrom, an automatic switch, a second trunk line terminatin in said automatic switch, a

third trunk line in parallel, a source of cur-,

rent for said circuit, means at the operators In a telephone system, an operators" an automatic switch, a second trunk relay in said circuit irresponsive to normal v cuit for controllin said switch by way of said second trunk ine,'a signal at said. op-

- erators position, a relay in said circuit irresponslve to normal current therein for controlling said signal, a second source of current and means for includmg said second source 1n said c1rcuit to increase the current flow therein to operate said relay.

18. In a telephone system, a calling line, an o erators position, and a trunk line accessi le therefrom, means at the operators position for connecting said calling line and trunk line, a called line, an automatic switch, a second trunk line terminating in said automatic switch having access to said called line, a third trunk lme inductively connecting said first and second trunk lines, a circuit including two conductors of said third trunk line in parallel, a source of ourrent'for said circuit, means in said circuit for controlling said switchby way of said second trunk 11ne, means including said first trunk line for controlling said circuit from the operators position, whereby saidswitch may "be operated to connect with the called line, a signal at the operators position, a

current therein for controlling said signal, a second source of current and means for including said second source in said circuit to increase the current flow therein to operate said relay.

19. In a telephone system, an operators position and a trunk line accessible therefrom, an automatic switch, a second trunk line terminating in' said automatic switch, a third trunk inductively connecting the two, a circuit including two conductors of said third trunk line in parallel, a source of current for said circuit, means at the operators pos1t1on for controllmg sald circuit by way of said first trunk line,-means in said,

circuit for controlling said switch by .way of said second trunk line, a 'signalat said operators position, a relay in said circuit irresponsive to normal current therein for controlling said slgnal, and means for increasmg the current flow in said circu t to operate said relay,-said last means including arelay in bridge of said second trimk line.

20. Ina telephone system, a calling line, an operators position and a trunk line accessible therefrom, means-at the operators position for connecting said calling line and trunk line, a called line, an automatic switch, a second trunk line terminating in said automatic switch havin access to said called line, a third trunk l1ne inductively third trunk line in parallel, a source of current for said circu t, meansin said circuit for controlling said switch by way of said second-trunk lme,means including said first trunk line for controllin said circuit from theoperators position, w ereby said switch may be operated to connect with the called line, a signal at the operators position,.a relay in sald c1rcuit irresponsive to normal current therein for controlling said signal,-

and means for increasing'the current flow in said circuit to operate said relay, said last means including a relay in bridge of said second trunk line.

. 21. In a telephone system, a calling line, an operators position and a trunk line accessible therefrom, means at the operators position for connecting said calling line and trunk line, a called line, an automatic switch, a second trunk line terminating in said automatic switch having access to said called line, a third trunk line inductively connecting said first and second trunk lines, a circuit including two conductors of said third trunk line in parallel, a source of current for said circuit, means in said circuit for controlling said switch by way of said second trunk line, means including said first trunk line for controlling said circuit from Ashe operators position, whereby said switch may be operated to connect with the called line, a signal at the operators position, a relay in said circuit irresponsive to normal current therein for controlling said signal, and meanscontrolled from the connected called line'for increasing the current flow in said circuit to operate said relay.

22. In a telephone system, means for connecting calling and called lines comprising a trunk line having an automatic switch at both ends, an operating circuit for said switches superimposed upon talking conducntors of said trunk line, a source of current for said circuit, means controlled by an operator for connecting 'a calling line with said trunk' line at either end, means controlled by said operatorfor operating said switch at the other end to connect with a called line, a supervisory signal for indicating to said operator the condition of the said called line, normally inoperative means in said circuit for controlling said signal, and

means for increasing the current flow in said circuit to operate said signal con-trolling means.

23. In a telephone system, means for connecting calling and called lines comprising a trunk line having an automatic switch at both ends, an' operating circuit for said switches superimposed upon talking conductors of said trunk. line, a source of current for said circuit, means controlled by an operator for connecting a calling line with sald trunk line at either end, means controlled by said operator for operating said switch at the other end to connect with a called line,a supervisory si nal for indicatin to said operator the cOHdItlOII of the said ca led said second source in said circuit to increase the current flow therein to operate said signal controlling means.

24. In a telephone system, means for connecting calling and called lines comprising a trunk line having an automatic swltch at both ends, an operating circuit for said switchessu erimposed upon talking conductors of sai trunk line, a source of current for said circuit, means controlled by an o orator for connecting a calling line with said .trunk line at either end, means controlled by said operator for operating said switch at the other end to connect with a called line, a, supervisory signal for indicating to said operator the con ition of the stud called line, normally inoperative means in sald c1rcuit for controlling said signal, and means controlled from the connected calledline for increasing the current flow in said clrcult to operate said signal controlling means.

25. In a trunking system, a pair of conductors, a first bridge across sald conductors, a second bridge across sald conductors, means for closing a third bridge across said first and second bridges, a source of current included in said third bridge a first relay associated with said third brldge, a line, an automatic progressively movable switch, means for controlling said first relay over said third bridge to operate said switch to find said line, a second relay assoclated with said third bridge, a signa associated with said second relay, said second relay normally inoperative, a second source of current and means controlled over said line for introducing said second source in said third bridge whereby said second relay may be operated to control said signal.

. 26. In a trunking system, a pair of conductors, a first bridge across said conductors, a second bridge across said conductors, means for closing a third bridge across said first and second bridges, a source of current in said third bridge, a first line, a second line, means controlled over the first line for controlling said first relay over said third bridge to operate said switch to connect the two .lines by way of said conductors, a sec-. ond relay associated with said third bridge, a signal associated with said second relay, said second relay normally inoperative, a

, second source of current and means controlled over said second line for introducing said second source in said third bridge whereby said second relay may be operated to control said signal.

27. In a telephone trunking system, a first circuit and a first automatic switch associated therewith, a second circuit and a second automatic switch associated therewith, a two conductor trunk line inductively connecting said circuits, a third circuit including the two conductors of said trunk line in parallel, a source of current for said circuits, a relay in the third circuit at one end for controlling said first switch, a relay in the third circuit at the other end for controlling said second switch, relays in the first and second circuits for controlling the third circuit, supervisory signals associated with said first and second circuits, supervisory control relays associated with said first and second circuits and adapted for inclusion in said third circuit, and means for closing said first circuit to operatethe relay included therein whereby the third circuit 1s completed by way of the supervisory control' relay for the first circuit and the controlling relay for the second switch.

28. In a telephone trunking system, a first circuit and a first automatic switch associated therewith, a second circuit and a second automatic switch associated therewith, a two conductor trunk line inductively connecting said circuits, a third circuit including the two conductors of said trunk line in parallel, a source of current for said circuits, a relay in the third circuit at one end for controlling said first switch, a relay in the third circuit at the other end for controlling said second switch, relays in the first and second circuits for controlling the 7 third circuit, supervisory signals associated with said first and second circuits, supersecond automatic switch associated therewith, a two conductor trunk line inductively connecting said circuits, a third circuit including the two conductors of said trunk line in parallel, a source of current for said circuits, a relay in the third circuit at one end for controlling said first switch, a. relay in the third circuit at the other end for controlling said second switch, relays in the first and second circuits for controlling the third circuit, supervisory signals associated with said first and second circuits, supervisory control relays associated with said first and second circuits and adapted for inclusion in said third circuit, and means for closing'either said first circuit or said second circuit to operate the relay included 1 its therein, whereby the third circuit is completed by wayfof the supervisory control relay for the circuit closed and the controlling relay for the switch associated w1th the other circuit. y Y

30. In a telephone trunking system, a first said second switch, relays in the first and second circuits for controlling the third circuit, supervisory signals associated with said first and second circuits, supervlsory control relays associated with said first and second circuitsand adapted for. inclusion in said third circuit, means for closing said first circuit to operate the relay included therein whereby the third circuit is completed by way of the supervisory control relay for the first circuit and the controlling relay for the second switch, and means in the first circuit for intermittently interrupting the same whereby said second switch may be operated.

31. In a telephone trunking system, a first circuit and a first automatic switch associated therewith, a second circuit and a second automatic switch associated therewith, a two conductor trunk line inductively connecting said circuits, a third circuit 1ncluding the two conductors of said -trunk line in parallel, a source of current for said circuits, a relay in the third circuit at one end for controlling said first switch, a relay in the third circuit at the other end for controlling said second switch, relays in the first and second circuits for controlling the third circuit, supervisory signals associated with said first and second circuits, supervisory control relays associated with said first and second circuits and adapted for inclusion in said third circuit, means for closing said second circuit to operate the relay included therein whereby the third circuit is completed by way of the super visory control relay for the second circuit and the controlling relay for the first switch, and means in the second circuit for interruptingthe same whereby said first switch may be operated.

32; In a telephone trunking system, a first circuit and a first automatic switch assos ciated therewith, a second circuit and a second automatic switch associated therewith, a two conductor trunk line inductively connecting said circuits, a third circuit including the two conductors of said trunk line in parallel, a-source of current for said cir cults, a relay in the third circuit at one end for controlling said first switch, a relay in the third circuit at the other end for con-' trolling vsaid second switch, relays .in the with said first and second circuits, supervisory control relays associated with said first and second circuits and adapted for I inclusion in said third circuit, means for closing either'said first circuit or said second circuit to operatethe rela included there in, whereby the third circuit is completed by way of the supervisory control'relay for the circuitlclosed and the controlling relay. for

the switch associated with the other circuit,

and means for interrupting the closedfirst or second circuit whereby the said second or first swltch may be operated.

33. In a telephone trunking system, a'first circuit and a first automatic switch asso-- ciated therewith, a second circuit and a second automatic switch associated there- -visory control relays associated with said first. and second circuits and adapted for inclusion in said third circuit, means for closing said first circuit to operate the relay included therein whereby the third circuitis completed by way of the supervisory control relay for the first circuit and the controlling relay for the second switch, said supervlsory control relay remaining inoperative, means in the first circuit for intermittently interrupting the same whereby said second switch may be operated, and means in the controlling circuit of the second switch for increasing the flow of current in the third'circuit to operate said supervisory control relay.

34:. In a telephone trunking system, a first circuit and a first automatic switch associated therewith, a second'circuit and a second automatic switch associated there with, a two conductorv trunk line inductively connecting said circuits, a third circuit including the two conductors of said trunk line in parallel, a source of current for said circuits, a relay in the third circuit at one end for controlling said first switch, a relay in the third circuit at the other end for controlling said second switch, relays in the,

first and second circuits for controlling the third circuit, supervisory si als associated with said first and second circults, su ervisor and second circuits and adapted for inclusion in said third circuit, means for closing said second circuit to operate the relay included therein whereby the third circuit is completed by way of the supervisory control relay for the second circuit and the controlling relay for the first switch, said super-v visory control relay remainln inoperatlve, means in the second circuit 'or interrupting the same whereby said first switch may be operated, and means in the controlling circuit of the first switch for increasing the flow of current in the third circuit to operate said supervisory control relay.

35. In a tele hone] trunking system, a

first circuit an a first automatic switch associated therewith, a second circuit and a second automatic switch associated there with, a two conductor trunk line inductively connecting said circuits, a third circuit including the two conductors of said trunk line in parallel, a source of current for said circuits, a rela in the third ClI'CUlt. at one end for controllin said first switch, a relay in the third circult at the other end for controlling said second switch, relays 1n the first and second circuits for controll.1ng the third circuit, supervisory signals associated with said first and second circu ts, supervisory control relays associated wlth said first and second circuits and adapted for inclusion in said third circuit, means for closin said first circuit to operate the relay inclu ed therein whereby the third circuit is completed by way of the supervisory control relay for the first circu1t and the controllin relay for the second switch, sa1d supervlsory control relay remaining inoperatlve, means in [the first c1rcu1t for intermittently interruplting the-same whereby said second switc may be operated, and means including a relay in the second switch for increasing the flow of current 1n sa1d *third circuit to operate said supervisory control relay.

36. In a telephone trunking system, a first circuit and a first automatic switch associated therewilth, a second circuit and a second automatic switch associated therewith,

a two conductor trunk line inductively connecting said circuits, a third circuit including the two conductors of said trunk l1ne 1n parallel, a source of current for sald c1rcuits, a relay in the third c1r c111t at one end for controlling said first c1rcu1t, a relay in the third circuit at the other end for controlling said second switch, relays in the first and second circuits for controlling, the third circuit, supervisory signals associated with said first and second circuits, super-- visory control relays associated with said first and second circuits and adapted for incontrol relays associated with sai first flow of current in said third circuit to operate said supervisory control relay.

37 In a telephone trunking system, a first c1rcu1t and a first automatic ond automatic switch associated therewith, a two conductor trunk line inductively connectmg said circuits, 9, third mg the two conductors of said trunk line in parallel, a source of current for said cirswitch associated therewlth, a second circuit and a seccircuit includcuits, a relay in the third circuit at one end" for controlling said first circuit, a relay in the third, circuit at the other end for controlling sald second switch, relays in the first and second circuits for controlling the th 1rd circuilt, supervisory signals associated w 1th sa1d first and second circuits, supervisory control relays associated with said first and second circuits and adapted for inclusion in said third circuit, means for closmg either said first circuit or said second c1rcu1t to operate the relay included therein, whereby the third circuit is completed by way of the supervisory control relay for the c1rcu1t closed and the controllin relay for the switch associated with the ot er circuit, said supervisory control relay remainin inoperative, means for interru tin the c osed first or second circuit where y t e said second or first swi' tch may be'operated, and means including a relay in the operated first or second switch for altering the current flow in said third circuit to operate said supervisory control relay.

38. In a trunking system, a first circuit, a

second circuit, a trunk line inductively connecting said circuits, a third circuit including the two conductors of said trunk line in parallel, a source of current for said cir cuits, a relay in said first circuit for controlling said third circuit, a second relay in said third circuit for controlling said second circuit, a si nal associated with said first circuit, and cans including a third relay in saidthird circuit for controlling said signal,

39. In a trunking system, a first circuit, an automatic progressively movable switch, a second circuit including a controlling magnet for said switch, a trunk line inductively connecting said circuits, a third circuit including the two conductors of said trunk line in parallel, a source of current for said circuits, a relay in said first circuit for controlling said third circuit, a second relay in said third circuit for controllingsaid second-circuit, a signal associated with said first circuit, and means including a third rela-y'in said [third circuit for controlling said signal; j

40. In a trunking system, a first circuit, a second circuit; a trunk line inductively connecting said circuits, a third circuit including the two conductors of said trunk l1ne 1n parallel, asource of current for said oncuits, a relay in said firstc1rcu1t for controlling said third circuit, a second relay in said third circuit "for controlling said second circuit, a signal associated with sa1d first circuit, a third relay in sa'd first-c rcult for controlling said-signal, and means including 7 a fourth relay in" said third circuit for altering the currentflow in said first c1rcu1t for controlling said third relay. L 41-. In a trunking system, a first circuit, an automatic progressively movable switch, a second circuit including a controlling magnet for'said switch, a trunk line inductively connecting said circuits, a third circuit 1ncluding the two conductors of said trunk line in parallel, a source of current for saidcircuits, a relay in said first circuit for 30. controlling said third circuit,'a second r elay in said third circuit for controll ng said second circuit, a signal associated w1th said first circuit, a third relay in said first c1rcuit for controlling said signal, and-mea ns including a fourth relay in said third c1rcuit for altering the current flow in said first circuit for controlling said third relay. 42. In a trunking system, a first circuit,

a second circuit, a trunk line inductively connecting said circuits, a third circuit including the two conductors of said trunk line'in parallel, a source of current for said circuits, a relay in said first circuit for controlling said third circuit, a second relay in said third circuit for controlllng s a1d second circuit, a signal associated" with sa1d first circuit, a third relay in said first cir-:

cuit for controlling said signal, means including a fourth relay in said third circuit for altering the current flow in said first cir- --"'{I- cuit for controlling said third relay, and a "fifth relay in said'second circuit for alterng the current flow in said third circuit for ontrollin'gsaid fourth relay. "trunking system,

a first circuit,

' an automatic progressively movable switch, a second circuit including a controlling ma t for said switch, atrunk line inductive y connecting said circuits, a third circuit including the two conductors of said trunk line in parallel, a source of current for said circuits,-a"-re1ay in said first circuit for controlling said hird circuit, a second relay in said third circuit for controlling said sectrolling said fourth relay.

ond circuit, a signal associated with said first circuit, a third relay in said first circ111t for controlling. said signal, means including a fourth relay in said third circuit for altering the current flow in said first cir-.. cult for controlling said third relay, and a, fifth relay in said second circuit for altering the current flow in said third circuit for conlet. In a trunking system, a first circuit, I a second circuit, a trunk line inductively connectlng said circuits, a third circuit in clud ng the two conductors of said trunk l ne m parallel, a source of current for said CII'GllllJS, a relay in said first circuit for controlling said third circuit, a second relay in 0 said third circuit for controlling said second c rcuit, a signal associated with said first circuit, means including a third relay in said third circuit for controlling said signal, a second source of current and means for. in- 5 troducing said second source in said third clrcuit to alter the current flow therein to operate said third relay.

45. In a trunking system, a first circuit,

an automatic progressively movable snitch,

a second circuit including a controlling magnet for said switch, a trunk line inductively connecting said circuits, a third circuit including the two conductors of said trunk line in parallel, a source of current for said circuits, a relay in said first circuit for controlling said third circuit, asecond relay in said third circuit for controlling said second circuit, a signal associated with said first circuit, means including a third relay in said third circuit for controlling said signal, a second source of current and means for introducing said second source in said third circuit to alter the current flow therein to operate said third relay.

46. In a trunking system, a first circuit, a second circuit, a trunk line inductively connecting said circuits, a third circuit including the two conductors of said trunk line in parallel, a source of current for said circuits, a relay in said first circuit for controlling said third circuit, a second relay in said third circuit for controlling said second circuit, a signal associated with said first circuit, means including a third relay insaid third circuit for controlling said signal, a second source of current and means for introducing said second source in said third circuit to alter the current flow therein to operate said third relay, said last means comprising a relay in said second circuit.

47.' In a trunking system, a first circuit, an automatic progressively movable switch, a second circuit including a controlling magnet for said switch, a trunk line inductively connectin said circuits, a third circuit including t e two conductors of said trunk line in parallel, a source of current "for said 

